One key characteristic of mobile radio communication is the typically rapid and significant variations in the instantaneous channel conditions as illustrated for one user in a cell in FIG. 1a. There are several reasons for these variations. Frequency-selective fading will result in rapid and random variations in the channel attenuation. Shadow fading and distance dependent path loss will also affect the average received signal strength significantly. Further, the interference at the receiver due to transmissions in other cells and by other terminals will also impact the interference level. Therefore, radio communication fluctuates in speed (throughput), signal quality and coverage. The fluctuation may become even more pronounced in situations where a user terminal involved in a communication moves around in a cell, perhaps with a considerable velocity, and, as mentioned above, when there are many terminals competing for the available bandwidth in a cell.
The different parts of a transport network, also called the backhaul, which connects for example a base station to the rest of a network, could generally be said to be less variable than a radio interface, although the backhaul also may vary in available bandwidth and signal quality.
The throughput from a content providing server to a user terminal, or from a user terminal to a content server is a function of the throughput of all the involved parts of the communication chain between the server and the user terminal. Therefore, it may occur that one part of the communication chain has a momentary high available bandwidth, which is not fully utilised, since a preceding part of the communication chain has a lower momentary available bandwidth.
It has previously been proposed to use buffers or proxies in different parts of networks. An overview of state-of-the-art proxy solutions are summarised in “Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations” (RFC 3135).
One problem with existing solutions is that it is hard to optimise or at least improve the utilisation of the available bandwidth in different parts of a communication chain. The available capacity of certain parts of a communication chain may be underutilised.